At the risk of sounding "techie" advertised compression in those days was the optimum possible number. All parts vary and the actual compression ratio could be lower; 10.0:1 or 10.5:1. Deck height and compressed head gasket thickness affect it. The standard speed shop "bluprint" included decking the block to reach the advertised ratio. Standard rebuild practices such as boring cylinders or a valve job can reduce the ratio.

So is Cam 2 fuel or higher octane required for these motors if driven on the street today..If so, that going to be an expensive ride,,,

TMR

With the stock "30-30" cam, no; its late-closing intake valve bleeds off some cylinder pressure, reducing the DCR somewhat, and any stock 11:1 302 that won't run properly on pump premium simply isn't tuned properly. Aftermarket cams always close the intake valve sooner in the never-ending quest for more power, and all bets are off with aftermarket cams.